The surveying industry has been moving for at least a decade away from optically based survey reconnaissance to GPS based location verification and marking. The modern surveyor uses a handheld or tripod mounted device that includes an advanced GPS chipset, enabling such surveying devices to communicate with the GPS constellation of satellites and know its GPS location within approximately a few meters.
More recently, non-specialized consumer devices, such as cell phones and tablet computing devices, include GPS chipsets and use their own application software to receive GPS satellite messages, which enable the device to calculate its GPS location. As is known, a GPS enabled device has a receiver that uses messages received from GPS satellites to determine each satellite's position and the time the message was sent. What is received is the x, y, and z components of the satellite's position and the time sent by the satellite, which are designated as [xi, yi, zi, ti] where the subscript i denotes the satellite and has the value 1, 2, . . . , n, and where n is greater than 4. Four satellite messages is the minimum number that a reasonable GPS based location may be obtained by a consumer device. When the time of message reception indicated by the on-board clock of the GPS enabled device is tr the true reception time is tr+b where b is receiver's clock bias (i.e., clock delay). The message's transit time is tr+b+ti. Assuming the message traveled at the speed of light, c, the distance traveled is (tr+b+ti)c. Knowing the distance from receiver to satellite and the satellite's position implies that the receiver is on the surface of a sphere centered at the satellite's position and with the radius being the distance traveled. Thus the receiver is at or near the intersection of the surfaces of the spheres if it receives signals from more than one satellite. In the ideal case of zero errors, the receiver is at the intersection of the surfaces of these spheres.
The clock error or bias, b, is the amount that the receiver's clock is off. The receiver has four unknowns, the three components of GPS receiver position and the clock bias [x, y, z, b]. The equations of the sphere surfaces are given by:(x−xi)2+(y−yi)2+(z−zi)2+=([tr+b+ti]c)2, i=1, 2, . . . , n or in terms of pseudoranges, pi=(tr+ti)c, aspi=√{square root over ((x−xi)2+(y−yi)2+(z−zi)2)}{square root over ((x−xi)2+(y−yi)2+(z−zi)2)}{square root over ((x−xi)2+(y−yi)2+(z−zi)2)}−bc, i=1, 2, . . . , n. 
The pseudoranges can then be solved to yield the GPS coordinates of the device. Using modern semiconductor processors, consumer devices can produce a series of GPS coordinates every second, from a plurality of satellite messages.
However, GPS based consumer devices lack sufficient precision to support serious surveying work on tracts of land. For example, the best consumer devices provide precision down to about 6 meters, but that precision is typically not maintained over relatively small sampling periods, resulting in variances of up to 30 meters. Such precision levels do not support services to survey or confirm land tract boundaries.
What is needed is a process and method for providing sufficient accuracy on handheld consumer devices that utilize standard low cost commercial GPS receivers, and preferably to provide consistent location accuracy to within one (1) meter or less.